Basically yes. According to Dann_Boeing's post in this thread, it may also be caused by too much stuff in your Lua.

Lorul1 wrote:It's not crashing the online or single play versions which is good

It indeed is, but this error should be taken as a warning. From my experience, when the BF2_ModTools starts to crash with the String Pool error it means you're close to hitting the limits of the retail version of the game.